1. Field of the Invention
The present invention relates to an autonomic-nerve-function evaluating apparatus which can easily evaluate function or activity of autonomic nerve of a living subject.
2. Related Art Statement
When a person who has functional disorder of autonomic nerve, such as autonomic imbalance, stands up, the person may show, e.g., a symptom of orthostatic hypotension, i.e., a large blood-pressure decrease. When functional disorder of autonomic nerve, or orthostatic hypotension is diagnosed, a blood-pressure value of a patient is iteratively measured after the patient stands up from a lying position, and a trend of changing of the thus measured blood-pressure values is recorded on a recording medium. Concurrently, a position of the patient is iteratively detected, and the thus detected positions are also recorded on the recording medium. This autonomic-nerve evaluation is carried out by, e.g. the apparatus disclosed in Japanese Utility Model Document JITSU-KAI-SHO No. 60-83603 and Japanese Patent Document TOKU-KAI-HEI No. 5-200030.
The above-described, conventional autonomic-nerve-function evaluating apparatus requires the patient to take a special resting position for the purpose of reading only blood-pressure changes caused by the standing-up load, or needs to employ a considerably large mechanism for the purpose of tilting a bed on which the patient lies, from its horizontal position to its vertical position, and thereby applying the standing-up load to the patient. Thus, the conventional apparatus is not easy to use and accordingly it has not been widely used yet.
It is therefore an object of the present invention to provide an autonomic-nerve-function evaluating apparatus which can easily evaluate function of autonomic nerve of a living subject.
In the above-identified background, the Inventors have carried out extensive studies, and have found that when inferior and superior limbs of a living subject are pressed for, e.g., measuring respective blood-pressure values of the inferior and superior limbs and thereby measuring an inferior-and-superior-limb blood-pressure index of the subject, heart rate and pulse pressure of the subject are transitionally influenced or changed by the pressing. It is speculated that those changes are caused by the autonomic nerve of the subject that functions, responsive to the load temporarily applied to the circulatory organ of the subject, to cause the circulatory organ to positively send blood and thereby recover the flow of peripheral blood in the inferior and superior limbs. Thus, the Inventors have found that it is possible to evaluate or inspect activity of autonomic nerve of a living subject by utilizing the above-indicated phenomenon, i.e., by utilizing respective changes of heart rate and pulse pressure of the subject when inferior and superior limbs of the subject are pressed using cuffs to apply load to the circulatory organ of the subject, without needing to require the subject to take a special resting position or without needing to employ a considerably large-size mechanisms for tilting a bed on which the subject lies. The present invention has been developed based on these findings.
The above object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for evaluating a function of an autonomic nerve of a living subject, comprising a heart-rate measuring device which iteratively measures a heart rate of the subject; a cuff-pressure changing device which changes a pressure in a first cuff adapted to be wound around an inferior limb of the subject, and a pressure in a second cuff adapted to be wound around a superior limb of the subject, so as to press the inferior and superior limbs; and a dispersion-degree determining means for determining a first degree of dispersion of the heart-rate values iteratively measured by the heart-rate measuring device after the cuff-pressure changing device starts pressing the inferior and superior limbs.
According to this aspect, the dispersion-degree determining means determines the first degree of dispersion of the heart-rate values measured by the heart-rate measuring device after the cuff-pressure changing device starts pressing the inferior and superior limbs of the subject. Since the degree of dispersion of the heart-rate values indicates the activity of the function of the autonomic nerve of the subject, the function of the autonomic nerve can be easily evaluated based on the degree of dispersion of the heart-rate values, without needing to require the subject to take a special resting position or without needing to use a considerably large-size mechanism for tilting a bed on which the subject lies.
According to a preferred feature of the first aspect of the present invention, the dispersion-degree determining means determines a second degree of dispersion of the heart-rate values iteratively measured by the heart-rate measuring device before the cuff-pressure changing device starts pressing the inferior and superior limbs, and the apparatus further comprises an evaluating means for evaluating the function of the autonomic nerve of the subject based on a change of the first degree of dispersion from the second degree of dispersion.
According to this feature, the activity of the autonomic nerve of the subject can be evaluated based on an amount or rate of change of the first degree of dispersion of the heart-rate values measured after the pressing of the inferior and superior limbs of the subject, from the second degree of dispersion of the heart-rate values measured before the pressing. Thus, individual differences are removed and accordingly a very accurate evaluation can be made.
According to another feature of the first aspect of the present invention, the dispersion-degree determining means determines, as the first degree of dispersion, a variance of the heart-rate values iteratively measured by the heart-rate measuring device.
According to this feature, the function of the autonomic nerve can be easily evaluated based on the variance "sgr"HR2 of the heart-rate values, without needing to require the subject to take a special resting position, or use a considerably large-size mechanism for tilting a bed on which the subject lies.
According to a second aspect of the present invention, there is provided an apparatus for evaluating a function of an autonomic nerve of a living subject, comprising a pulse-pressure measuring device which iteratively measures a pulse pressure of the subject; a cuff-pressure changing device which changes a pressure in a first cuff adapted to be wound around an inferior limb of the subject, and a pressure in a second cuff adapted to be wound around a superior limb of the subject, so as to press the inferior and superior limbs; and a dispersion-degree determining means for determining a first degree of dispersion of the pulse-pressure values iteratively measured by the pulse-pressure measuring device after the cuff-pressure changing device starts pressing the inferior and superior limbs.
According to this aspect, the dispersion-degree determining means determines the first degree of dispersion of the pulse-pressure values measured by the pulse-pressure measuring device after the cuff-pressure changing device starts pressing the inferior and superior limbs of the subject. Since the degree of dispersion of the pulse-pressure values indicates the activity of the function of the autonomic nerve of the subject, the function of the autonomic nerve can be easily evaluated based on the degree of dispersion of the pulse-pressure values, without needing to require the subject to take a special resting position or use a considerably large-size mechanism for tilting a bed on which the subject lies.
According to a preferred feature of the second aspect of the present invention, the dispersion-degree determining means determines a second degree of dispersion of the pulse-pressure values iteratively measured by the pulse-pressure measuring device before the cuff-pressure changing device starts pressing the inferior and superior limbs, and wherein the apparatus further comprises an evaluating means for evaluating the function of the autonomic nerve of the subject based on a change of the first degree of dispersion from the second degree of dispersion.
According to this feature, the activity of the autonomic nerve of the subject can be evaluated based on an amount or rate of change of the first degree of dispersion of the pulse-pressure values measured after the pressing of the inferior and superior limbs of the subject, from the second degree of dispersion of the pulse-pressure values measured before the pressing. Thus, individual differences are removed and accordingly a very accurate evaluation can be made.
According to another feature of the second aspect of the present invention, the dispersion-degree determining means determines, as the first degree of dispersion, a variance of the pulse-pressure values iteratively measured by the pulse-pressure measuring device.
According to this feature, the function of the autonomic nerve can be easily evaluated based on the variance "sgr"PP2 of the pulse-pressure values, without needing to require the subject to take a special resting position, or use a considerably large-size mechanism for tilting a bed on which the subject lies.